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. 2006 Jan 26;114(4):567–572. doi: 10.1289/ehp.8700

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One carbon metabolism pathway. Abbreviations: 5MTHF, 5-methyltetrahydrofolate; THF, tetrahydrofolate. The availability of methyl groups for DNA methylation is increased by provision of excess methyl donors and cofactors, including folate, choline, and SAM, which is the major methyl donor for DNA, RNA, protein, and lipid methylation.